Soggy crops presented 2013 insect control challenge

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• Combine the higher than usual populations of plant bugs, with usually high stink bug populations, lower than expected corn earworm populations, early fall armyworms and kudzu bugs and growers found more and more problems getting the right insecticide on at the right time to take care of different combinations of these pests.

Plant bugs often over-looked

Plant bugs are often over-looked because the adult of the species can move from place to place very rapidly.

Unlike many pests of cotton, both plant bug adults and nymphs can damage the crop and when the final yield and quality assessments are in, it’s likely there will be much more damage from plant bugs than in most years.

Because of their rapid movements in and out of cotton fields, and subsequently of adjacent grain fields, and the difficulty in sampling for these insects, some growers tried preventative applications of neonicotinoid insecticides to take out plant bugs and the first generation of stink bugs.

Applied in mid- to late-June in Virginia and northern areas of North Carolina, the treatment was successful and economical at about $3 per acre when using low rates of insecticide.

Herbert said spraying for an insect that may not be in the field is not a good idea for at least two reasons.

“First, the grower in most years will be paying for something he or she doesn’t need. This year, the conditions were good for plant bug populations to thrive, but in most years we are much more prone to drought and heat than to rain and cool, cloudy weather,” he said.

Perhaps more importantly, the Virginia IPM leader said there are distinct indications that resistance to neonicotinoid insecticides is building in several pests for which these sprays are used.

When there is a sample and thresholds are there, then growers need to use these insecticides, Herbert said.

Reisig adds, “For example, Centric is a popular neonicotinoid insecticide that provides very good aphid control. As a result, it is widely used in many cotton growing areas of the Southeast.

“In tests using Centric and another neonicotinoid insecticide, Belay, Reisig said they are already seeing reduced control with Centric.”

He added that both Centric and Belay, combined with a pyrethroid like Swagger and Endigo provided good control of plant bugs and stink bugs.

“Transform is a new material that is similar in mode of action to the neonicotinoid insecticides, but has a different active ingredient and does not pose a threat to increasing neonicotinoid resistance.

“When growers are sampling for most insects, plant bugs in particular, they need to remember the differences between adults and nymphs. The nymphs will sit in the field and feed for extended periods of time, but the adults can move in and out of a cotton or corn field very quickly,” Reisig said.